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Amplitude and frequency

To calculate the frequency , you divide 1 by this time period. For example, the graph of the shrill sound of a whistle will look a lot more bunched up than the graph of the deep sound of a double bass. The sound represented by the green line in the graph below would have a higher pitch than the sound represented by the purple line.

Of course, most sound waves are not pure like the ones shown above, because most sounds are made up of combinations of lots of waves. By contrast, speech is a combination of multiple sound waves of different frequencies and amplitudes that results in a more complicated wave. With free software like Audacity and a microphone connected to your computer maybe as part of a webcam , you can record different sounds and look at the shape of the sound wave.

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Search Search. Unable to play video. Please enable JavaScript or consider upgrading your browser. View transcript. Vibrations and waves Sound is all about vibration. Whistling As you can see, whistling produces a smooth, simple sound wave. Speech By contrast, speech is a combination of multiple sound waves of different frequencies and amplitudes that results in a more complicated wave.

Activity: record and investigate sound waves With free software like Audacity and a microphone connected to your computer maybe as part of a webcam , you can record different sounds and look at the shape of the sound wave. Give it a try — record sounds and noises produced by items in your home. Can you tell anything about the sounds by looking at the waves on screen? Share your observations in the comments! More courses you might like Learners who joined this course have also enjoyed these courses. Learn how to start a career in games development by hearing from leading games producers, recruiters and new developers.


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  5. University of York. F4 and F5 affect the timbre of the voice, but have little influence on which vowel is heard Sundberg, We repeat below the plots of F2,F1 for two accents of English. Note that, in these graphs, the axes do not point in the traditional Cartesian direction: instead, the origin is beyond the top right corner.

    Andrei Linde: 2013 Fundamental Physics Prize Speech

    This choice maintains that tradition approximately. These maps were obtained in a web experiment, in which listeners judge what vowel has been produced in synthetic words Ghonim et al. Experiment : using that web site you can make a map of the vowel plane of your own accent.

    Transcribing words

    We repeat the figure showing the vowel planes for US and Australian English measured in an on-line survey Ghonim et al. The vocal tract as a pipe or duct To understand how the resonances work in the voice, we can picture the vocal tract from the glottis to the mouth as a tube or acoustical waveguide. It has approximately constant length, typically 0. However, the cross section along the length varies in ways that can be varied by the geometry of the tongue, mouth etc. The frequencies of the resonances depend upon the shape. The frequencies of the first, second and i th resonances are called R1, R2,..

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    See this link for a discussion of the terminology. When pronouncing vowels, R1 takes values typically between Hz small mouth opening to Hz. Increasing the mouth opening gives a large proportional increase in R1. Opening the mouth also affects R2, but this resonance is more strongly affected by the place at which the tongue most constricts the tract. Typical values of R2 for speech are from about to Hz. The resonant frequencies can also be changed by rounding and spreading the lips or by raising or lowering the larynx Sundberg, ; Fant, Similarly, reducing or enlarging the cross section near a pressure node respectively lowers or raises the resonance frequency.

    Conversely, reducing or enlarging the cross section near a pressure anti-node respectively raises or lowers the resonance frequency. This explains some features of the tongue constriction. The nasal tract has its own resonances, and the nasal nose and buccal mouth tracts together have different resonances. The lowering the velum or soft palate couples the two, which affects the spectral envelope of the output sound Feng and Castelli, ; Chen, Nasal vowels or consonants are produced by lowering the velum or soft palate, see Figure 1. The nasal tract also exhibits resonances.

    Coupling the nasal to the oral cavity not only modifies the frequency and amplitude of the oral resonances, but also adds further resonances. Resonances, frequency, pitch and hearing Some comments about frequency and hearing are appropriate here.

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    The voice pitch we perceive depends largely on the spacing between adjacent harmonics, especially those harmonics with frequencies of several hundred Hz Goldstein, For a periodic phonation, the harmonic spacing equals the fundamental frequency of the fold vibration, but the fundamental itself is not needed for pitch recognition. Except for high voices, the fundamental usually falls below any of the resonances, and so is often weaker than one of the other harmonics.

    However, its presence is not needed to convey either phonemic information or prosody in speech. The pass band of telephones is typically about to Hz, so the fundamental is usually much attenuated. The loss of information carried by frequencies above Hz e.

    Their fundamental frequencies are not carried by the telephone line. Can you hear their pitch? Of course, the are less 'bassy' than if you heard them live, but is the pitch any different? Our hearing is most sensitive for frequencies from to Hz. Consequently, the fundamentals of low voices, especially low men's voices, contribute little to their loudness, which depends more on the power carried by harmonics that fall near resonances and especially those that fall in the range of high aural sensitivity.

    Another experiment : you can test your own hearing sensitivity on this site. Timbre and singing Varying the spectral envelope of the voice is part of the training for many singers. They may wish to enhance the energy in some frequency ranges, either to produce a desired sound, to produce a high sound level without a high energy input, or to produce different qualities of voice for different effects.

    Characteristic spectral peaks or tract resonances have been studied in different singing styles and techniques Stone et al. In this laboratory, we have been especially interested in three techniques: resonance tuning , harmonic singing and the singers formant. The origin of vocal tract resonances Vocal tract resonances Ri give rise to peaks in the output spectrum Fi. However, the relation between Ri and Fi is a little subtle. This section follows Wolfe et al, Below, it is modelled as a simple cylindrical pipe to explain, only qualitatively, the origin of the first two resonances.

    The dashed line is for a cylinder. This figure is taken from Wolfe et al A pressure p at the lips is required to accelerate a small mass of air just outside the mouth, so the inertance is not zero, but is usually Z rad small.

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    Physics , The Physics of Music and Speech

    At high frequency, however, larger accelerations are required for any given amplitude, so Z rad increases with frequency. In a confined space inside the vocal tract , acoustic flow does not spread out, so impedances are usually rather higher than Z rad. As we explain in this link , Z in a pipe or in the vocal tract depends strongly on reflections that occur at open or closed ends. A strong reflection occurs at the lips, going from generally high Z inside to low Z in the radiation field. Suppose that a pulse of high-pressure air is emitted from the glottis just when a high pressure burst pulse returns from a previous reflection: the pressures add and Z is high.

    Conversely, if a reflected pulse of suction cancels the input pressure excess, Z is small. This effect produces the large range of Z shown in the previous figure. High output levels occur at the lips when the input impedance Z is a minimum. Now, for a simple tube with length L, open at the far end, the behaviour is shown by the dashed line in the preceding figure. Minima occur half way between the maxima. The solid line shows the new input impedance Z. The maxima in Z pressure antinodes or flow nodes are hardly changed.


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    This makes sense: a local constriction of small volume at the input has little effect on a maximum in Z , where flow is small. For modes where the flow is large, however, the air in the glottis must be accelerated by pressures acting on only a small area. So the frequencies of the minima in Z pressure node, flow antinode fall at lower frequencies. If the glottis is sufficiently small, Z f falls abruptly from each maximum to the next minimum, which thus occur at similar frequencies.

    So do the maxima in the transfer functions. This is difficult to measure. However, there are good reasons to expect no strong resonances in the audio frequency range. The lungs have complicated geometry, with successively branching tubes, extending to quite small scale at the alveoli. This is expected to produce little reflection in the range of frequencies that interest us see Fletcher et al. As mentioned above, many of the obvious experiments for studying vocal tract resonances are impossible. A number of less obvious techniques exist, however.

    One of our papers reviews these Wolfe et al, As we explained above, the resonances of the vocal tract occur at frequencies well above those of the fundamental frequency — at least for normal speech and low singing. Further, the frequencies of vocal fold vibration which gives the voice its pitch and those of the tract resonances which determine the timbre and, as we have seen, the phonemes are controlled in ways that are often nearly independent.

    In most singing styles, the words and melody of a song are prescribed. Conversely, in speech, we have the subjective impression that we can vary the prosody independently of the phoneme — for example, one can often replace a key word in a sentence without changing the prosody at all. In the voice, there is usually no simple relation between the frequencies: a singer may cover a range of two or more octaves i. Further, although there is typically a difference of an octave a factor of two in wavelength between the fundamental frequencies of male and female singing voices, there is much smaller difference in the lengths of the tracts.

    From this we can conclude that the resonances of the tract do not normally control the pitch frequency of the voice. Nevertheless, the glottal source and the vocal tract resonances may be interrelated in a number of ways.